In a surrogacy arrangement, a woman agrees to carry someone else's baby for a fee, which is usually between $20,000 to $25,000 for a single fetus. The egg and sperm can come from the couple who hire the surrogate, or a donor egg or sperm are used.

Sometimes parents know their surrogate -- she might be a sister or a friend. Other times the parents meet the surrogate through an agency.

Surrogates and intended parents must be well matched, says Melissa Brisman, who practices reproductive law in New Jersey and runs a surrogacy agency.

Elizabeth Cohen

For example, if parents feel strongly they would terminate the pregnancy if a fetal abnormality were found, they shouldn't be matched with a surrogate who is adamantly opposed to abortion.

"You want to flesh out those issues and make sure you're on the same page," Bisman says.

Serious conflicts between surrogates and intended parents are relatively rare; Brisman estimates that out of thousands of surrogate pregnancies, only about a dozen have ended up in court.

But when problems do arise, as in Kelley's case, the ending can be disastrous. Kelley says she assumed the parents were, like her, against abortion because the mother said her frozen embryos were her "babies" and she had to give them a chance at life. But when the fetus Kelley was carrying turned out to have birth defects, the parents wanted to abort and she didn't.

Here are her tips for having a surrogacy arrangement with a happy ending.

1. Each side should have an attorney

The surrogate and the intended parents should each have their own lawyer review the contract.

2. Understand the limits of the contract

Even if the surrogate signs a contract agreeing to abortion if there's a fetal abnormality, she can later change her mind. "You can't force her to have an abortion," Brisman says.

3. Agree on prenatal testing

Sometimes intended parents want an amniocentesis but the surrogate doesn't want the test, which would involve having a needle stuck in her stomach. The two sides should come to an agreement before the pregnancy takes place.

4. Have a full psychological evaluation

In Brisman's practice, the surrogate and intended parents sit together for five or six hours to have a full discussion on many issues, including abortion.

Kelley said the intended parents weren't present at her evaluation, which was done over the telephone. The subject of abortion never came up, she added. She said the evaluation was done by Rita Kron, who works at Surrogacy International, the agency that arranged the surrogacy.

That's a problem, Brisman says. A person who works for the agency stands to benefit financially if the surrogacy goes through, and might be tempted to overlook potential conflicts that could kill the deal.

CNN contacted Surrogacy International, and a woman who said her name was Rita answered the phone. "You have to understand something -- there is a privacy that exists and that's the end of the story," she said and then hung up. Kron did not return CNN's e-mails.

5. Understand the relationship after birth

Will the surrogate pump breast milk for the baby? Will the parents send photos of the baby as he or she grows up? Can the surrogate contact the parents for updates? All of these questions should be worked out beforehand, Brisman says.